Screw-threaded stock and manufacture of same



K. BERGER SCREW-THREADED STOCK AND MANUFACTURE OF SAME March 14, 1939.

Filed Sept. 50, 1937 JIIIIPN u INVENTOR KORNEL BERGER BY AT ORNEY i I 4 I l 1 i mas-aim 31 Patented Mar. 14, 1939 SCREW-THREADED STOCK AND MANU- FACTURE F SAME Kornel Berger, Brooklyn, N. Y.

Application September 30, 1937, Serial No. 166,511

12 Claims.

The invention herein disclosed relates to screwthreaded stock and to manufacture of the same.

Particularly, the invention is concerned with the manufacture of running thread nipples, pipe nipples and other forms of screw-threaded tubing and to the manufacturing and the threading of such tubing.

Special objects of the invention are to improve screw-threading operations in general; to accomplish manufacture of tubing from sheet material and the screw-threading of same by practical, eflicient and low cost methods and to provide running thread nipples and other forms of screwthreaded tubing of desirable characteristics and inexpensive form.

Other objects and the novel features of the invention by which the foregoing and other desirable objects are attained are set forth in the following specification, illustrated in the accompanying drawing and broadly covered in the claims.

In the drawing these are illustrated certain practical embodiments and present preferred methods of manufacture. Structure and modes of operation, however, may vary as regards the immediate disclosure, as will be apparent from the true spirit and broad scope of the invention as hereinafter defined and claimed.

Figs. 1, 2 and 3 are perspective views illustrating successive stages in manufacture of the tubing from flat stock.

Fig. 4 is a broken plan view illustrating passage of the tubular stock between the thread rolling dies.

Fig. 5 is an end view of the stock passing between the dies.

Fig. 6 is a broken view as on substantially the line 6-6 of Fig. 5.

Fig. '7 is a perspective view showing the length of tubular stock as formed into a running thread nipple.

Fig. 8 is a brokenpart sectional longitudinal view illustrating another form of thread rolling dies.

Fig. 9 is an end view of this second form of die construction.

Fig. 10 is a broken perspective detail showing the notching of the end of the tube for holding same against rotation in passage between dies such as last illustrated.

Fig. 11 is a broken detail showing the end of the tubing serrated, scalloped or toothed for engagement with corresponding holding means.

Fig. 12 is a side view of a running thread nipple formed from tubing having serrated matching edges.

Fig. 13 is a similar view of a pipe nipple formed from tubing having an interlocked seam.

The tubing for running thread nipples, pipe nipples and other relatively short lengths may be provided, under this invention, as indicated in Figs. 1, 2 and 3, by taking a. blank of fiat stock such as shown at IS in Fig. 1 and after passing it through a U-ing die to double it as in Fig. 2, rolling, curling or bending the edges together as in Fig. 3, to complete the-tubular structure I6. As shown in the latter view, the edge portions may be bent inward beyond the arc of a true circle to an extent such that upon release of the pressure of the bending dies, the metal will return to substantially circular form.

The edges of the tube may be made to firmly abut or be left slightly separated and be left unattached as indicated in Fig. 3, or be positively connected or interlocked. The rolling of the screw threads strengthens the material and in that way largely is responsible for enabling the manufacture of. running thread nipples and the like, from tubularly formed blanks having unattached edges or open seams.

For the sake of more accurately and completely abutting the opposite edges of the stock along this seam, the opposite edges of the blank may be bevelled to an extent such as indicated at ll, such that in the rounding action they will come fully into abutment, as in Fig. 3.

The rolling of the screw-threads is accomplished by effecting passage of the tubular stock between thread rolling dies having annular, as distinct from the usual helical screw-threading ridges and which dies are mounted for rotation on axes inclined to the axis of the stock on substantially the helix angle of the screw thread to be formed. In practice, the stock may travel through between the rolls, or the rolls be made to traverse the stock or the relative movement may be a combination of both.

Figures 4, 5 and 6 illustrate the method of thread rolling by three dies l8, I9, 20,'spaced equidistantly about a common axis 2|, representing the axis of the stock l6. and having each a series of annular, circular thread rolling ridges 22, in parallel relation in accordance with the spacing of the screw threads to be formed.

As perhaps best shown in Figure 4, these thread rolling dies are journaled on axes 23, inclined to the stock axis 2|, on an angle substantially corresponding to the pitch angle of the screw thread.

These thread rolling die; may be journalled on fixed centers, in which event, the shafts 24 of the rolls are driven to rotate them in unison and the stock is introduced between them and is rotated -and advanced at the rate of the screw-threading operation.

As an alternative, such screw forming rolls may be mounted on a rotating carrier as indicated at 25, Figures 8 and 9, which will carry them while rotating, bodily about the stock and which stock will then be held against rotation but be permitted to travel longitudinally between the rolls, or the rolls be caused to travel longitudinally over the stock.

One method of holding the stock against rotation, for the second type of operation described, is to provide it with notches in one end, as indicated at 26, Figure 10, to engage corresponding lugs on' a non-rotating mandrel serving as a guide and holder for the stock. Instead of notches the stock may have projecting lugs to engage in notches in the mandrel or holder. The equivalent of this is illustrated in Figure H, where the end of the stock is serrated all the way around at 21 to form teeth or alternate lugs and notches for engagement with corresponding alternate notches and lugs on a guiding and holding mandrel.

The thread rolling dies, as shown in Figs. 4, and 6, may have end roll portions 20, in front of the thread forming ridges to operate as guides for directing the stock into the bite of the ridges.

These guide roll portions may be knurled, toothed or roughened as indicated at 29, and the relative spacing of the rolls be such as to make these guide roll portions exert pressure on and in the case of knurled rolls, actually bite into and positively grip the stock.

The tips of the gripping roll portions may be spaced a slightly greater diameter than the external diameter of the stock, so that the stock may be readily entered therebetween and such spacing be tapered down to an extent where the roll surfaces will grasp and sufllciently grip or bite into the stock to rotate and advance the stock with a screw-like action substantially corresponding to the helix angle inclination of the annularly ridged thread rolling dies.

The ridged portions 01' the rolls are spaced a diameter less than the external diameter of the stock, so as to roll the thread 3|], up on the outside of the stock increasing the overall diameter to such extent.

In Figs. 4, 5, and 6, the axes of the rolls are inclined so as to bring the intermediate thread rolling ridges of the rolls closest together, thus to effect a progressive thread rolling action, with The same considerations apply in the bodily ranged dies illustrated in Figures 4, 5 and 6 have rotating form of thread rolling dies shown "in Figs. 8 and 9, the main distinction simply being that in the latter instance, the dies have a bodily turning movement about the stock, which is held against rotation, instead of remaining on fixed centers, while the stock rotates, as in the first embodiment. A cam, screw or equivalent means may be provided in the second form of the ap the thread rolling dies, such cam or screw then constituting the equivalent of the feeding means described in connection with the first form of apparatus. If the bodily rotating dies are advanced over the stock, or if a combination of longitudinal stock movement and longitudinal movement of dies is used, such in either event would be considered feeding means equivalent to that first disclosed.

The cold rolling of the screw threads by building up the diameter of the rolled sheet stock has a stretching and extending eiiect tending to bridge and knit the metal across the open seam and to such extent consolidating and unitying the structure. This working of the metal also actually strengthens the material. As a result, running thread nipples for example, constructed in accordance with this method are as strong or in some cases stronger and serve every purpose of the more expensive seamless tube or cut thread nipples. In the thread rolling operation, no metal is removed and the working of the metal in building up the screw threads has such a strengthening effect that relatively thin and inexpensive sheet metal can be used.

This screw rolling method is applicable to the screw threading of one or both ends, intermediate portions, or the continuous full length screwthreading of any tubular or solid stock. For part length screw-threading operations, the dies are made to automatically separate at the end of the desired screw length. Where both ends of the stock are threaded, the stock may be held at some central point and be simultaneously threaded at both ends. Where intermediate portions are to be threaded, the dies may be first opened up to take the stock and then be closed, while the stock is held at one or both ends.

The angularity of the rolls relative to the axis of the stock gives the rolls a certain approach on the stock, enabling the gripping end portion to grasp and then firmly take hold of the stock and the first met ridges to start with a comparatively light screw forming impression followed by gradually deeper impressions of succeeding thread forming ridges. Because of these gradual and successive thread forming operations, the stock is not subjected to any extreme crushing action or strain and hence is not deformed even though the seam is left open or unattached. The circular or annular thread rolling ridges work across the open seam of the stock at an angle or inclined instead of directly across at a right angle and this inclined application of energy has a tendency to keep the seam closed or to close it the more firmly, instead of opening it.

Because of the natural self-centering efiect,

' three thread rolling dies are at present considered the most desirable, but a greater or less number may be employed. These are set so that the thread rolling effect of one is taken up and continued by the other or others, with the thread rolling action of the ridges on one coinciding with and continuing the thread rolling action of the others. The three substantially horizontally arthe efiect of feeding in, threading and discharging the threaded stock. The rolls however can be arranged on substantially vertical or inclined axes so that the feeding movement and discharge of the stock will be assisted by gravity.

Instead of leaving the seams of tubular stock open or unattached, the edges of the rolled material may be partially or wholly-interlocked or secured.

Thus as shown in Fig. 12, the opposite edges may be notched or toothed, so as to interlock as a serrated or corrugated seam 3|.

As another form, the edges may be fully interlocked and secured with a dovetail form of joint as indicated at 32, in Fig. 13.

Fig. 13 illustrates also the feature of making pipe nipples or equivalent structures by this invention. In this view, a length of tubular stock is shown having tapered screw threads 30a, rolled in the opposite ends of the same, such taper being the result of the progressive thread rolling action following from the angular setting of the thread rolling dies previously described.

The tubing may be of cylindrical or other cross-sectional form and may be seamless or have open seam unattached edges as first disclosed, or the edges may be attached, as with a lock seam or the like. The screw-threading may be carried out on continuous lengths of tubing, pipe or solid stock of cylindrical or other crosssectional shape and such stock after threading, may be subsequently cut in any desired lengths.

The expressions screw-thread or screw-threading or thread or threading have been used synonymously as referring to any forms of screwthread, such as pipe thread, tapered thread, single or parallel thread, or the like.

The stepped relation of the thread rolling dies may be effected by having the die rolls all alike and offsetting each one in advance or in rear of the adjoining roll, or by mounting them all in approximately the same circular relation about the stock axis and having them with the thread rolling ridges of one stepped in advance or in rear of the next adjoining roll. While usually practical to make these die rolls as separate elements fixed on the shafts which rotate them, it is considered that they may be mounted to rotate on supporting shafts and be turned on those supporting shafts by suitable gearing.

Instead of forming the tubular blanks by U- bending flat stock and then curling the edges of the doubled stock toward each other, as illustrated, other methods of forming the generally flat material into tubular shape may be employed and the description as to rolling the stock or mention of the tubes as rolled are intended to cover such possible variations of bringing the more or less flat stock material into the desired tubular shape.

In practice of the invention, it has been found that a half hard stock, that is something harder than what is known as soft stock, steel for instance, is desirable. Because of the inherent spring in the half hard stock, it is at present considered desirable to curl the edges of the tubular blank inwardly past the true circle, so that on release of the bending pressure, the material will assume substantially circular form. Then the guiding, gripping and screw-threading rolls will act evenly and uniformly on the stock. Particularly with such truly circular or substantially circular stock the guiding and feeding-in portions of the rolls may be smooth and the rolls be set inwardly sufficiently to exert a firm and positive pressure on the stock. This pressure grip form of feed may be preferred to the knurled, roughened or toothed type of grip. In the latter instance, where the engagement is one of more or less biting into the stock material, the rolls need not be set so closely together, since they may not be required to actually exert a compressive pressure on the stock.

The terms flat stock and the like have been used to indicate any form of what is generally known as sheet material suitable for the purpose, 5 such as rolled strip, flat rolled sheets andt-ltlike.

Each of the die rolls is shown as having a plurality of screw rolling ridges all of the same diameter.

It has been shown that open seam or unatm tached tubing may be employed and that the edges of the tubing may be attached or secured together. Such attachment may be continuous such as accomplished by welding or some form of interlock be employed. The extent of such 15 attachment or interlocking may vary. Thus as illustrated in Fig. 13, a complete non-separable form of interlock may be employed or as shown in Fig. 12 the interlock may be of a partial nature, such as will prevent relative longitudinal 2U movement of the edge portions, but not positively prevent separation on a transverse axis.

The feeding-in rolls are shown as integral with and actually part of the screw-threading rolls.

It has been shown that the stock may move be tween the rolls or the rolls be caused to move over the stock and that there may be relative movement of both stock and screw threading rolls, so passage of the stock between the rolls in any of such ways is within the scope of the invention.

It is intended that all possible modifications such as mentioned shall be covered in the claims.

What is claimed is:

1. As a new article of manufacture, a running thread nipple, composed of flat stock bent into tubular form with the edges in opposition but with an open seam between them and an external rolled screw thread extending the length of the nipple across said open seam. 40

2. As a new article of manufacture, tubing composed of flat stock bent into tubular form with the edges opposed but left with an open seam between them and screw threads rolled into the exterior of said tubing across said open seam.

3. The method of forming screw-threaded tubing, which comprises bending flat strip stock into tubular form with the edges in opposition and then rolling external screw threads progressively along the length and across the open seam between the edges of said tubular stock.

4. The method of manufacturing screwthreaded tubing, which comprises bending flat stock into tubular form with the edges opposed but disconnected and then entering said tubular stock between dies spaced about a common center a distance less than the radius of the tubular form to which said fiat stock has been bent having circular thread rolling ridges and rotating said dies about the stock on axes inclined to the axis of the tubular stock at an angle corresponding to the pitch angle of the screw thread to be formed. I r.

5. Apparatus for screw-threading tubular stock comprising thread rolling dies having annular thread rolling ridges and mounted in spaced relation about a common axis on axes inclined to said common axis at an angle corresponding to the pitch angle of the threads to be rolled, said dies being spaced with the thread rolling ridges 7 separated a diameter less than that of the outside diameter of the stock and said dies having guide roller ends in front of said thread rolling ridges and in relatively spaced relation tapering from a diameter greater to a diameter less than the outside diameter of the stock and means for effecting relative rotation of said thread rolling dies and stock'and relative longitudinal travel of the dies and stock.

6. As a new article of manufacture, a tubular member of sheet material having aligned projections and recesses on the opposite edges of the same and having said edges brought together in tubular formation and interlocked against relatively endwise displacement by engagement of projections in one edge in recesses in the opposite edge and screw threads rolled on the exterior of said member over the interlocked seam so provided.

a '7. The method of forming screw-threaded tubing, comprising the steps of U-bending flat stock and then bending the separated edges of the stock inwardly toward each other and past a true circle to an extent sufliclent for the material to return to substantially circular outline when the bending force is released and then rolling said substantially circular tubular stock between thread rolling dies having circular thread rolling ridges spaced apart less than the circumference of said circular stock and inclined to the axis of the stock on angles substantially corresponding to the pitch angle of the screw thread to be formed.

8. Apparatus for forming a screw thread, comprising thread rolllng dies each having an annular thread rolling ridge and mounted in spaced relationabout a common axis on axes inclined to said common axis at an angle corresponding to the pitch angle of the screw thread to be rolled and stock feeding-in rolls in front'of said threading rolls and rotating on substantially the same inclined axes as said thread rolling dies.

9. As a new article of manufacture, a running thread nipple composed of rolled strip stock bent into tubular form with the edges in opposition but unattached and screw threads rolled into the exterior of said tubular rolled strip extending the length of the same across said unattached edges.

10. As a new article of manufacture, a running thread nipple composed of flat stock bent into tubular form with the edges in opposition but unattached and having an external screw thread rolled in the same between three or more substantially equidistantly spaced dies and across said unattached edges.

11. As a new article of manufacture, a running thread nipple composed of flat stock bent into tubular form with the edges in opposition but unattached and having an external screw thread rolled along the length of the same across said seam by three or more thread rolling dies.

12. The method of screw-threading tubular stock,-which comprises providing thread rolling dies with annular thread rolling ridges and with guide rollers of lesser diameter in front of said thread rolling ridges, mounting said dies and guide rolls spaced about a common center a distance to receive the tubular stock between the guide rolls, and on axes inclined to the axis of the stock at an angle substantially corresponding to the pitch angle of the screw thread to be rolled in the stock, rotating said' dies and guide rolls on said axesand entering said tubular stock between said guide rolls in advance of said annular thread rolling ridges.

KORNEL BERGER. 

